The present invention relates generally to a bobbin tube, and more particularly to a bobbin tube which is especially suited for use in filament winding apparatus of the type having automatic bobbin-changing mechanisms, but which can also be employed otherwise.
Filament or thread winding apparatus is well known in the art. It utilizes one or more bobbin winding chucks which are rotatable and which usually can be moved into and out of engagement with the periphery of a drive roll, so that the chucks are surface driven. The chucks are generally cylindrical and bobbin tubes of paper or another material are slipped onto them and can then rotate with the chuck. A filament is supplied to the chuck from a supply, in some instances directly from an apparatus for producing synthetic plastic filaments, and is wound onto the bobbin tube to form thereon a filament package or cop.
In modern winders of this type, which must be capable of high-speed operation and preferably should operate continuously, automatic bobbin-changing mechanisms are provided which, when a yarn package or cop has been fully formed on a bobbin tube, move the bobbin tube with the yarn package thereon from the chuck and replace it with a new empty bobbin tube. One type of prior-art apparatus operating on this principle uses a pivoted arm carrying at each end one of the chucks so that, when a bobbin tube with a full yarn package is removed from one of the chucks, the arm is tilted so that the bobbin tube on the other chuck in the meantime is in contact with the drive roll and receives filament from the same. By the time the yarn package has built up on this previously empty bobbin tube, the package on the other chuck has been replaced with a new empty bobbin tube which is now ready to be in turn brought into contact with the surface of the drive roll.
In this type of apparatus, difficulties have been encountered in transferring the yarn or filament from the completed package which is running by contact with the drive roll, to the empty bobbin tube that is on the other chuck. It is known to provide the bobbin tubes with a notch or similar detent, to capture the yarn which moves axially of the bobbin tube, or else to provide adhesive means on the bobbin tube for the same purpose. However, neither of these possibilities has to be found to be particularly advantageous, and especially where a so-called bunch winding is required on the bobbin tube, that is where the yarn must not immediately begin to traverse axially of the bobbin tube but is first required to form a number of convolutions in one spot before the traversing and subsequent buildup of the package begins, the problem of making the yarn remain at such a location that the buildup of the bunch winding can be completed, has not been satisfactorily solved in the prior art.
Moreover, the expedients which have been used in the prior art, for instance the application of adhesive strips to the outer surface of the bobbin tube, have the additional disadvantage of making the tubes difficult to handle and, at least in the case of adhesive strips, of being usable only once and having to be replaced for the next operation.